La

2

SO

6

(LS)

Gd

2

SO

6

(GS) and Y

2

SO

6

(YS) were prepared by a flux method in a reducing atmosphere. They are of the same type of structure

orthorhombic

with the space group I

222

and the site Symmetry of

Ln

is C

2

.The luminescence of Ce

3+

in them was studied v/ith their excitation spectra and emission spectra.The spectra of GS:Ce

3+

and YS:Ce

3+

are quite similar as expected

whereas those of LS:Ce

3+

show marked differences.The excitation spectra of the samples prepared by codoping Ce

3+

and another emission center which can be sensitized by Ce

3+

e.g. Dy

3+

in these three hosts monitored at Dy

3+

emission line

show very similar behavior (Fig.2).The excitation peaks due to Ce

3+

in GS:Ce

3+

Dy

3+

and YS:Ce

3+

Dy

3+

coincide with those of GS:Ce

3+

and YS:Ce

3+

in Fig.1

whereas the peaks located at-300nm and-330nm in LS:Ce

3+

Dy

3+

have no correspondence in LS:Ce

3+

. But it was argued that these two peaks also originated from Ce

3+

and this was affirmed by diffused reflection spectrum of LS:Ce

3+

(Fig.3).Hence the luminescence of Ce

3+

in LS might be described as following:the 5d manifold of Ce

3+

are split into 5 levels

in conformity with C

2

site symmetry

three of them are obtained directly from the excitation spectra of LS:Ce

3+

the other two are obtained from the excitation spectra of a center sensitized by Ce

3+

or from the deffused reflection spectra and the emission is originated from the next lowest 5d state.Here it can be argued that two factors pertaining to the appearance of the uncommon emission from the next lowest 5d state are as follows. (1) small Stokes’ shift

and (2) narrower excitation peaks.